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# Mechanics help watch

1. Your uncle works at the railroad freight yard, and he has asked you to watch the yard hands couple 30,000-kg boxcars together. As he leaves to get a sandwich, he tells you, "Whatever you do, don't let those cars bang together too hard. Each coupling will take only 3,000 J on a hit before it shatters." You ask how hard is too hard, but your uncle has already ducked out.

I did 3000= 0.5(30000)v^2 and solved for v but apparently my answer is wrong. Is there something Im missing out on the question?
2. (Original post by liemluji)
Your uncle works at the railroad freight yard, and he has asked you to watch the yard hands couple 30,000-kg boxcars together. As he leaves to get a sandwich, he tells you, "Whatever you do, don't let those cars bang together too hard. Each coupling will take only 3,000 J on a hit before it shatters." You ask how hard is too hard, but your uncle has already ducked out.

I did 3000= 0.5(30000)v^2 and solved for v but apparently my answer is wrong. Is there something Im missing out on the question?
I presume that the cars are loose, and so on collision won't come to a standstill, but rather continue in motion - conservation of momentum.

Looks like an American question.

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